1. Field of the Invention
The present invention relates to a display in which a plurality of fine discharge tubes, each of which is divided into sections which can individually emit light, are combined, and which utilizes electric discharge.
2. Description of the Related Art
A large display, in which a fluorescent phosphor is activated by ultraviolet rays generated by electric discharge so that visual light is emitted, and in which the size of the display can be freely designed, is disclosed in Japanese Unexamined Patent Application Publication No. 2000-315460. This display, which is shown in FIGS. 15 and 17 in the above-described publication, includes a plurality of display tubes (discharge tubes) arranged in parallel to each other and a substrate which support the discharge tubes. Each of the discharge tubes includes a glass tube into which a discharge gas is filled and island-shaped display electrodes are arranged on the external surface of the glass tube in the longitudinal direction of the glass tube. In addition, a long data electrode is disposed on the internal surface of the glass tube in such a manner that the data electrode opposes all the display electrodes. Two display electrodes which are adjacent to each other with a predetermined distance therebetween function as a pair of discharge electrodes for surface discharge. Island-shaped metal bus electrodes are arranged on the substrate in pairs in such a manner that the metal bus electrodes intersect the data electrodes, and the display tubes are disposed on the substrate in such a manner that the display electrodes individually contact the metal bus electrodes. Each metal bus electrode crosses, all the display tubes and connects the group of display electrodes which belong to the same level to each other. Thus, an electrode matrix is formed by the group of display electrodes and the group of data electrodes. An arbitrary image can be displayed by controlling the voltages supplied to the electrode matrix by a method similar to a voltage control method used in a typical three-electrode surface-discharge plasma display panel.
Through the development of the discharge tubes disclosed in the Japanese Unexamined Patent Application Publication No. 2000-315460, the inventors have found the following facts. A case is considered in which a display is constructed by arranging the display electrodes on the external surface of the discharge tubes and forming the metal bus electrodes through which voltages are supplied. If the display has low resolution, the positional relationship between the display electrodes and the metal bus electrodes does not cause a problem. However, if the display has high resolution, the accuracy of the positional relationship between the display electrodes and external electrodes is severe since pitch allowance between the electrodes are accumulated over the display area. For example, if 1000 display electrodes having a width of 300 xcexcm are arranged with 1 mm pitch, the maximum allowance in the relative position may exceed the width of the electrodes unless the allowance in the relative position corresponding to a single electrode is 0.3 xcexcm or less. Accordingly, there is a problem in that it is technically difficult, and a considerably high cost is incurred, to realize such a high positional accuracy.
In addition, when each of the discharge tubes has a circular shape in cross section, the distance between the discharge electrodes and the fluorescent phosphor is approximately the same as the inside diameter of the discharge tube. Thus, vacuum ultraviolet rays generated by electric discharge are absorbed by the discharge gas before they reach the fluorescent phosphor, thus reducing the luminous efficiency.
In order to solve the above-described problems, the inventors have invented a display which includes discharge tubes having an elliptical shape, and more preferably, a flattened elliptical shape, in cross section. Accordingly, the required positional accuracy can be reduced and the luminous efficiency can be improved.
According to one aspect of the present invention, an AC-type gas discharge display comprises a base; a plurality of discharge tubes which are arranged on the base in parallel to each other and which contain fluorescent phosphors; data electrodes formed on the external surfaces of the discharge tubes such that the data electrodes extend in the longitudinal direction of the discharge tubes; and display electrodes formed in pairs, in each of which one display electrode serves as a scanning electrode and the other display electrode serves as a common electrode, on the external surfaces of the discharge tubes at the opposite side from the data electrodes such that the display electrodes intersect the discharge tubes. Each of the discharge tubes has a flattened elliptical shape in cross-section thereof and includes a pair of flat portions. The data electrodes are formed on one of the flat portions and the scanning electrodes and the common electrodes are alternately arranged on the other one of the flat portions, and the discharge tubes are supported by the base at one or the other one of the flat portions.
The wall thickness of each discharge tube is preferably 400 xcexcm or less at least at one of the flat portions and a gas discharge occurs between adjacent pairs of display electrodes in each discharge tube via the corresponding part of the wall.
In addition, width of the flat portion of each discharge tube is preferably larger than 0.3 mm.
According to another aspect of the present invention, an AC-type gas discharge display comprises a discharge tube into which discharge gas is filled, which is provided with at least one pair of display electrodes on the external surface thereof, which includes a fluorescent layer on the internal surface thereof, and which emits visual light when a gas discharge occurs therein. The discharge tube has an elliptical shape in cross-section thereof, and the display electrodes are disposed on the external surface of the discharge tube such that the display electrodes extend in the direction of the major axis of the elliptical shape.
At least a part of the discharge tube is preferably formed as a flat portion and the display electrodes are preferably formed on the flat portion of the discharge tube.
In addition, the discharge tube preferably includes a pair of flat portions which, in cross sectional view, extend in the direction of the major axis of the elliptical shape while opposing each other.
In addition, in the cross-section of the discharge tube the ratio of the major axis to the minor axis is preferably in the range of 10:7 to 5:1.
In addition, the display electrodes are preferably formed on one of the flat portions, and a fluorescent phosphor layer is preferably formed over the other one of the flat portions and curved portions formed at both sides thereof.
In addition, the fluorescent phosphor layer is preferably formed on a fluorescent phosphor layer supporter and the fluorescent phosphor layer supporter is inserted into the discharge tube.
According to the present invention, since the discharge tubes have a flattened elliptical shape in cross section, the discharge tubes can be stably disposed on a base, and discharge electrodes can be reliably arranged over a large area. In addition, the luminance and the luminous efficiency can be increased.